Stupidly simple memory monitoring script

watch_mem.sh

#!/bin/bash

# Tested on Ubuntu 8.04 32 bit
# When the memory limit drops below $memory_limit megabytes, bash will ring a bell
# and echo the current memory usage.

# Set the free memory limit (in megabytes)
memory_limit=150

# Check interval (in seconds)
interval=30

while true; do
	free_memory=`free -m | tail -2 | head -1 | awk '{print $4;}'`

	if (( $free_memory < $memory_limit )); then
		echo "Warning: memory is $free_memory!"
		echo $'\a'
	fi
	sleep $interval
done